Defroster for ice cube trays



@1.29, 194e. RHBQAKER *2,410,194

DEFROSTER FOR lICE CUBE TRAYS Filed May e, 1944 s sheets-sheet 2 :Suventor ajr Qttornegs @QL 29,1946. R H BAKER 2,410,l94

' DEFROSTER FOR ICE CUBE TRAYS Filed May 6, 1944 5 Sheets-Sheet 5 n Mmvsm (Ittornegs Patented Oct. 29, 1946 kUNITED STATES PATENT oFFice DEFROSTER FOR ICE CUBE TRAYS Robert H. Baker, Munster, Ind.

2 Claims.

The present invention relates to improvements in defrosters for freezing units, ice cube trays, ice cubes and the like and to a novel method of defrosting the freezing unit, ice cube trays, ice cubes, etc., and more particularly relates to a heating element and the method of use of such element in refrigerators for the quick defrosting and easy removal of ice cube trays and ice cubes.

` An object of the invention is to provide one or more forms of simple andrinexpensive heating units which lend themselves readily to application to the freezing unit of an electric or other refrigerator in a position or positions where such heating unit, when activated, will melt or defrost the area in the Vicinity ,ofl the tray and its support so as `to permit the tray to be readily detached from the side walls of the freezing unit, from the shelf .upon which itrests and from its contact with adjacent trays, if any.

Another object of the invention is to suit the heating unit to the freezing unit with a minimum of reconstruction of the latter.

A further object of the invention is to so construct, constitute and arrange one or more heating units at opposite local positions in the freezing unit as to be effective for local defrosting in a minimum of time.

The invention alsocontemplates the use of a thermostat for automatically interrupting the circuit through the heating resistance wire after the lapse of a predetermined time period to avoid destructive action of the heat upon the refrigerant or the refrigerating unit and its parts.

The invention further contemplates a form of heating unit and radiating sheet in a new relationship to the refrigerant tubes and thermostat in a showcase type of store refrigerator.

With the foregoing and other objects in view, the invention will be more fully described hereinafter, and will be more particularly pointed out in the claims appended hereto.

In the drawings, wherein like symbols refer to like or corresponding parts throughout the several views,

Figure 1 is a perspective view of a refrigating unit of a conventional type showing the application of one form of the improved heating units thereto.

Figure 2 is Ya horizontal section taken on the line 2-2 of Figure 1.

Figure 3 is a perspective view, with parts broken away and parts shown in section, of one form of heating unit employed.

Figure 4 is a perspective view of a modified type Application May 6, 1944, Serial No. 534,447

2 of heating unit mounted in a tube indicated in broken lines.

Figure 5 is a View similar to Figure 1 showing a modified form of heating unit and its yapplication t0 a refrigerating unit of the refrigerator.

Figure 6 is a plan view of a further modified form of heating unit.

Figure '7 is a longitudinal section therethrough taken on the line 'l-l in Figure 6.

Figure 8 is a perspective View of the interior members of such heating unit.

lFigure'9 is an exploded view of the elements or members of this group.

Figure 10 is a modified form of heating element showing a three-member group.

Figure 1l is an exploded view of the three members. n

`Figure `12 is a longitudinal section taken through a `container with the threeV element group.

Figure '13 shows a further modified form of the heating element and an insulator support therefor.

Figure 14 shows the case for this form of heating unit.

Figure 15 is a fragmentary sectional view through a showcase type of store refrigerator having one of the improved defrosting elements applied thereto in connection with a metallic radiating sheet.

Figure 16 is a perspective view showing a diagrammatic preferred coil arrangement of the resistance heating wire with two terminals for convenience in plugging into a socket.

Referring more particularly to the drawings and for the present to Figures 1, 2 and 3, 2i) designates the freezing unit of a conventional form usually found in household refrigerators in which a rectangular metallic frame 2l is externally surrounded by refrigerant coils 22. Within the frame 2l the usual trays for the ice cubes may be introduced in a well known manner and supported either upon the bottom 23 of the frame or upon a shelf 24 or both.

In accordance with the present invention one or more heating units are applied to either the bottom 23, side walls of the frame `2"! or to the shelf 24 or to all of these parts as shown in Figure 1.

For this purpose the said bottom 23, shaft 24 and Side walls of the frame 2| are pressed outwardly along definitive lines to produce grooves 25 in which the heating elements may be placed.

One such heating unit is shown in Figure 3 as Comprising an electric resistance wire 26 embedded in a body of insulation 21 and encased in a copper or other metal tube 28.

A satisfactory form of heating unit has consisted of a 1A" copper tube 28 with the heating resistance wire 26 running axially through the tube and Wrapped with spun glass electrical tape which proved satisfactory for insulating the heating element from the copper tube. In the first instance the heating wire 26 was wrapped with the glass tape and thereupon inserted into the copper tube 2B while this tube extended in a straight line. Before any current was turned into the wire 26 the unit comprising Wire 26 wrapped tape 21 and copper tube 28 was bent to the desired curves and shapes. Thereupon the heating wire 26 was charged and the glass tape caused to fuse slightly which caused it to lose some of its pliability without sacrificing its ideal insulating qualities. The fusion caused the tape after several hours of continuous heat to consolidate into a cohesive and homogeneous insulating body 21 tending to unit wire 26 and tube 28. The spun glass tape, so fused, has qualities for lasting indefinitely. It is not desired to charge the element with electricity until the tube 28 has been bent to the desired shape.

As hereinafter described more particularly in connection with Figure 15, the circuit of the heating wire 26 may be controlled by a thermostat, or the wire 26 may be of predetermined resistance so that it heats to the desired temperature and will not rise destructively above the same.

When current is turned through the wire 26 the ice trays, although frozen tight, will be loose in a matter of a few minutes. It may take somewhat longer to free the ice cubes. After deenergizing the heating unit, the freezing unit will reestablish its freezing temperature in approximately ten minutes. The refrigerator can be defrosted while the door of the refrigerator is closed. The switch element should be designed so as to shut off the freezing unit when the defroster is in use. The element 26 should not be allowed to get too hot as this might become harmful. 1n larger refrigeration units, Where the cost would not be prohibitive an electrical clock or timer could be used that would automatically defrost the unit at the necessary intervals.

Referring more particularly to Figure 4 a modified form of the heating unit comprises a porcelain or other insulating solid core 29 with a helix 36 of electric resistance wire wound eX- ternally about the same and through V-shaped notches 3| in discs 32 of porcelain or other insulating material which are fitted about the core 2'8 at the ends and suitable intervals therealong. The discs are of greater diameter than the core 26 thus providing protected areas between the discs 32 for containing the wire 30. Further protection is obtained by the tubular shaped cover 33 which may be of copper similar to the cylinder 28 of Figure 3. A metal material for the parts 28 and 33 is desirable on account of the high conductivity of the metal which tends to transfer and distribute the heat generated from within the heating unit to the areas to be defrosted.

Referring more particularly to Figure the bottom, side walls and shelf of the freezing unit are compartmental as indicated at 34 and 35 to receive heating units composed of sheets 36 of mica prepared to receive therethrough the high resistance Wire 31. This Wire is passed through the perforations from one to the other side of the sheet 36. In other words it is threaded through the perforations. The sheets are held between blocks of insulating material 38.

Referring more particularly to Figures 6 to 9 inclusive, a still further modified form of heating element is shown consisting of four sheets of mica 36, 46, 4|, 42. An intermediate sheet 4| is reduced between its ends to receive the resistance wire coil 43. One end of the coil passes out through a perforation 44 of a companion sheet 46 and is thus brought out as one of the leads 45 of the element. The other lead 46 comes off the other end of the coil 43. The sheets 35 and 42 form enclosing members for the two intermediate sheets 46 and 4|. All four sheets can be very readily enclosed in a metal case composed of the half parts 41 and 48 with the ends 49 clipped together as shown in Figure 7. This element can be very easily installed in present day refrigerators and can be manufactured at very moderate cost. Two such elements would be sufficient, one under each ice tray, or placed at the sides of the tray.

Referring more particularly to Figures 10, l1 and 12, a very similar form of heating unit is illustrated having the three sheets 5U, 5| and 52 to make a still thinner unit in which sheets 56 and 52 are blank or imperforate and all are of mica or suitable insulating material. The intermediate sheet 5I is perforated as indicated at 53 to receive the resistance wire 54 which is run therethrough in the manner indicated in Figure 10. These three elements, in the order named are assembled into a metallic case 55 as shown in Figure l2.

Referring more particularly to Figures 13 and 14, 56 designates a sheet or plate of insulating material having perforated insulators thereon which support the coiled heating wire 58. This element is received into a metal case 59 with the mica sheet 56 acting as the cover for the case to enclose the heating unit.

Referring more particularly to Figure l5 this is a cross section of the freezing unit of a showcase type of store refrigerator. The freezing unit usually runs all the way across the front of the refrigerator although in some types there vis a freezing coil at each end of the showcase. The heating unit is of the type illustrated in Figure 3 and is designated generally at 28a. On account of its versatility this unit may be made to follow the freezing unit regardless of type or shape.

The heating element 23a generates heat for de*- frosting purposes. Its copper tube is in contact with the metallic sheet 66 which absorbs the heat, confines and distributes the heat directly to the refrigerant tubes or coils 6|. Heat from the element 28a radiates through the sheet 66 to the refrigerant tubes 6| and thermostat 62 at approximately the same ratio, making it possible to control the amount of heat which reaches the refrigerant tubes 6 I. It would not be necessary for the heat to reach a temperature of over 60 or 70 degrees. A drainage trough 63 is seated beneath l the heating unit 28a, distributing plate 60 and coils 6l' to carry off to a suitable vessel for easy removal the Water resulting from the defrosting operation.

The flat heating elements such as shown in Figures 6 to 12 inclusive can be manufactured very cheaply and can be usedk in every conceivable type of refrigerating unit without requiring any alterations whatsoever. It would simply raise the pan a quarter of an inch.

1n the claims wherever the word wire is used 5 it will be understood that it refers not only to a. wire but also to a coil, rod, bar or strip of material that generates heat.

It is obvious that various changes and modications may be made in the details of construction and design of the above specifically described embodiment of this invention without departing from the spirit thereof, such changes and modifications being restricted only` by the scope of the following claims,

What is claimed is:

1. A modied refrigerating evaporator for household refrigerators in which refrigerating coils surround a rectangular metallic frame having side walls, a bottom, a top and being without ends to admit slidable trays for ice cubes, the modification comprising pressed-out areas in the walls and bottom along denitive lines to produce grooves opening on the inner space of the unit, and heating coils lying in said grooves flush with the plane of the inner faces of the wall and upper face of the bottom.

2. The combination of claim 1 characterized by the fact that the heating coils are formed of tubes of metal having straight pieces of resistance Wire axially therethrough and wrapped with spun glass electrical tape fused throughout into a cohesive and homogeneous insulating mass between the wire and tube.

ROBERT H. BAKER. 

